The present invention relates generally to coating processes, and more particularly to such processes used for fabricating targets.
The attainment of lasing action at shorter and shorter wavelengths has been an on-going field of research with many anticipated applications.
The traditional laser consists of an active medium pumped in some manner to produce an inverted electron population density between two energy states, and inserted between mirrors which form an optical resonant cavity. A later discovery showed that intense laser emission could be obtained from systems without optical cavities. These highgain mirrorless systems have appropriately termed amplified spontaneous emission (ASE) systems. ASE systems are of major importance in short-wavelength lasers such a X-ray lasers where high reflectivity mirrors do not exist. To produce gain in ASE systems, high inversion densities are called for.
One source given serious consideration for pumping X-ray transitions is laser beams. For example, Nd.sup.+3 laser beams can be focused to small volumes with high irradiance. However, the photon energy is too small to pump X-ray transitions directly, so the high-power laser pulse must be used to vaporize and heat a pump material to generate plasma X-rays (and charged particles) which in turn fall onto a nearby lasing material and pump the latter's energy levels to inverted populations.
It is of great importance that the plasma X-rays from the pump material be collected efficiently for pumping the lasing material, i.e., over a large, solid angle. Hence the geometry of the target configuration is very important. That is, the thickness and congruency of layered slot targets as well as that of more confined and channeled-plasma targets similar to those described in commonly-assigned U.S. Pat. No. 4,206,364 is most important to maintain.
One promising system of pump material and lasing material under study is the neon-sodium system in which the Na X 1s.sup.2 1 S-1s 2p.sup.1 P line at 11.00 Angstroms is used to optically pump the Ne IX 1s.sup.2 1 S-1s 4p.sup.1 P line at 11.001 Angstroms creating an inversion primarly in the n=4, 3 and n=3, 2 level pairs of Ne IX, and stimulated emission at 230 and 82 Angstroms, respectively.
Sodium occurs naturally as a solid, but neon occurs naturally as a gas, making it difficult to fabricate the two materials in a controlled fashion into a target for plasma laser production.